Pressure core taker



: Patented Sept. 28, 1943 PRESSURE CORE TAKER Earl Babcock, Duncan, Okla., assignor to Halliburton Oil Well cementing Company, Duncan,

Okla.

Application December 17, 1941, Serial No. 423,351

3 Claims.

This invention relates to pressure core takers,

and more particularly to apparatus for securing a core of rock from an oil well or the like and sealing the same under the pressure prevailing at the time the core is taken.

As is well known to those skilled in the art, the

taking of cores of rock during the drilling of an oil well may be accomplished by dropping a core barrel down through'the drill pipe, the core barrel being so designed as to seat in the drill pipe and be rotated therewith to take a core, the barrel then being fished out by the use of a wire line.

It has also been proposed to provide a wire line operated core barrel with means for sealing the same in the well so that after the core is in the barrel, it may be brought to the surface without contamination. by th mud in the well;

The present invention relates tea-wire line core barrel having simple means for sealing and operating the same.

It is one object of the invention to provide a possible the amount of contamination of the core with mud fluid.

Other objects and advantages reside in certain novel features of the arrangement and construction of parts, as will be apparent from the following description taken in connection with the accompanying drawing, in which:

Figure 1 is a view in side-elevation, with certain parts broken away and others in cross-section, showing a wire line pressure core taker constructed in accordance with the present invention, in place in a drill "for taking a core in the bottom of an oil well;

Figure 2 is a view in side-elevation of a section of the core taker shown in Figure 1, showing the eccentricity of the valve chamber;

Figure 3 is a transverse-sectional view of the arrangement of Figure 1, the view being taken on the lines 3--3 of Figure 1; and s Figure 4 is an enlarged sectional view of a part of the apparatus of Figure 1, 'showing the details of mounting the core catcher.

Referring to the drawing in detail, it will be seen that a fragment of a drill pipe is shown at l I,

the pipe supporting a drill bit l2, which may be of the usual type employed in connection with a wire line core barrel. One section of the drill line prespipe may be provided with a latch ring l3 for. holding the core barrel in place in the bit.

In accordance with the present invention, a wire line core taker is vprovided which consists essentially of a heavy outer cylinder l4 and a light, or thin walled, inner cylinder l5, together with a suitable valve and latching mechanism.

The outer heavy cylinder H has a, suitable cap it threaded thereon at its upper end. Beneath this cap the cylinder I4 is provided with slots l'l, within which latch dogs I8 are'mounted on pivot pins i9, the dogs 18 being urged outwardly under the influence of suitable leaf springs 20.

The lower end of the cylinder I4 is threaded to make connection with a cutting cylinder 2 I, having a serrated lower edge 22. As is obvious'from the drawing, the cylinder 2| projects downwardly through an opening in the bit [2 and it is splined with the bit l2 so as to rotate therewith and cut a core.

Immediately above the cutting cylinder 2|, the outer cylinder 14 is provided with an eccentric circular ofiset valve housing 23, which is welded or otherwise rigidly connected to the cylinder l4, and which provides a chamber for a flapvalve 24 secured on an arm 25,pivoted to the cylinder l4 at 26. A torsion spring (not shown)i urges the arm 25 in a clock-wise direction, asviewed in Figure 1.

Immediately below the valve 24 the; cylinder 14 is provided with a valve seat 21, the seat being of the usual conical type. The valve 24 is preferably provided with a conical rubber sleeve,

' so as to aid in efiecting a tight seal.

At the lower part of the valve seat 21, there are oneor more mud escape ports 3i through the wall of the housing 23, the purpose of which will appear presently.

The inner cylinder l5 has an operating rod 28 integrally connected to its upper end. The rod passes upwardly from the cylinder 15 through a 'stuffingbox consisting of chevron packing 29, held in place between two annular nuts 30, threaded on the interior of the cylinder M.

The upper end of the operating rod 28 is provided with'the usual conical latch member 32 for making connection with a fishing tool. (not shown). such as an overshot. It is also provided with a shear pin 33 which normally connects the operating rod 28 and, hence, the inner cylinder l5 to the cap iii of the outer cylinder I4. The operating rod collar 34 for operating latch dogs l8.

Theinner cylinder I5 is provided with one 01 28 is also provided with a more slots 35 which serve to permit escape of mud fluid therefrom as a core is being taken and which also cooperate with splines 31 on the inner wall of cylinder I 4 to cause the two cylinders to rotate together at all times.

The lower end of the inner cylinder [5 is inwardly flanged so as to support a swivelled core catcher 31 near the valve seat 21 below the mud escape ports 3|.

The base of the core catcher 31 is preferably slightly larger in diameter than the inner diameter of the cutter cylinder 2| and slightly smaller in diameter than the cylinderv l5. The fingers of the core catcher 31 are, of course, diametrically spaced less distance than the inner diameter of the cylinder 2|. V

In accordance with the known practice, the outer cylinder H may be provided with means for making connection to a pressure gauge or to means for obtaining a sample of fluid therein after the core taker has been brought to the surface, but such means is not shown in the drawing.

The operation of the apparatus to take a core under pressure,is as follows:

With the cylinder l5 mounted in the outer cylinder l4 and secured by the shear pin 33, the core taker is dropped in the drill pipe and allowed to move downwardly until it is seated and latched in the drill, as shown in Figure 1.

With the-parts in this position, the valve 24 is held up by the inner cylinder IS. The drill is then operated in the usual way to cut the core and as the core is cut, it passes upwardly into the inner cylinder IS, the mud ahead-of the core in the cylinder l5 passing out through the slots 35 in cylinder and out through the mud escape ports 3! in cylinder M. In this operation, all the parts shown in the drawing except, the core catcher 31 rotate with the bit.

After the core has been cut, a fishing tool on a wire line is run into the drill pipe and latched onto the connector 32 of the operating rod 28. As the rod 32 is pulled upwardly, the pin 33 shears and the core is broken off at or below the core catcher 31 and lifted into the pressure cylinder l4 above the valve 24 by the rod 28 and cylinder l5.

This upward movement continues until the top of the cylinder l5 abuts against the lower packer holding nut 30. The mud within cylinder l4 above cylinder l5 passing downwardly through the annular space between the two cylinders into the valve chamber. There should not be much clearance between cylinders l4 and IE but enough to permit this fiow of mud.

Before the top of cylinder l5 strikes the lower packing ring 30, the lower end clears valve 24 so this valve closes. seals the ports 3|. There is enough space between the top of cylinder l5 and lower packing ring 30 to permit slightly more vertical movement of the rod 28, to insure tripping of the latch 18, but this space should be kept to a In closing, the valve 24" under high hydrostatic pressure, such as commonly prevails in the bottom of an oil well, and since when the core taker is brought to the surface, the pressure exterior of the cylinder I4 will be atmospheric, this cylinder must be extremely strong.

The inner cylinder IE, on the other hand, is not subjected to any pressure differential and need be only strong enough to transmit sulficient tension from the operating rod 28 to the core catcher 31 to break and take the core.

The prime object in taking a core under pressure is to avoid contamination of the core by mud as it is brought to the surface. To avoid entrapping a large quantity of mud with the core in the cylinder I4, the clearance between it and the inner cylinder l5 should be small and the chamber for the valve 24 should be as small as possible without interfering with the closing of the valve. It is also important because of the high pressure mentioned, to keep the diameter of the cylinder M as close to the diameter of the core as possible. It is for this reason, among others, that the valve housing 23 is constructed as shown.

It will. be seen that the arrangement illustrated provides an extremely simple construction, the main advantage over wire line operated pressure core takers previously proposed, residing in the use of only one valve and in the provision of a simple rod through a stuffing box for lifting the core into the pressure cylinder and tripping the latch which fastens the core taker to the drill pipe.

Only one embodiment of the invention has been shown and described herein. It is obvious that various changes may be made in the arrangement and construction of parts without departing from the spirit of the invention or the scope of the annexed claims.

I claim:

1. A wire line operated pressure core taker for oil well use, comprising an outer pressure cylinder having means for latching the same in drill pipe having a bit thereon, a single valve associated with said pressure cylinder for controlling the flow of fluid from said outer cylinder, an inner, core receiving and lifting cylinder fitted into said outer cylinder and normally occupying such relative position with respect thereto as to hold said valve open, releasable means for holding the inner and outer cylinders in said normal relative position so that the core taker may be dropped down through the drill pipe to seat in the drill, wire line operated means for lifting said inner cylinder upwardly into said outer cylinder to release said valve and for releasing said latching means, the arrangement being such that the valve is released before said outer cylinder is unlatched.

A wire line operated pressure core taker for use with-drill pipe in oil wells, comprising an outer pressure cylinder open at its lower end, an inner core receiving and lifting cylinder, telescopically mounted in said outer pressure cylinder, said inner cylinder also being open at its lower end and having a mud discharge aperture near its upper end, a rod attached to the top of said inner core receiving cylinder to move the same longitudinally with respect to said pressure cylinder, sealing means between said rod and said pressure cylinder, a single valve mounted on the lower end of said pressure cylinder, and means beneath said valve for discharging mud irorn the interior to the exterior of said outer pressure cylinder, the arrangement being such that as a core is cut and fed into said inner core receiving cylinder, mud may flow from said inner cylinder to said outer cylinder and thence down and out of said outer cylinder through said mud discharging means, whereas after the core is lifted, said valve prevents the flowv of fluid from the lower open end of said pressure cylinder and also through said mud discharging means.

3. A wire line operated pressure core taker for oil well use comprising an outer pressure cylinder, an inner core receiving and lifting cylinder,

means for latching the outer cylinder in drill pipe having a-bit thereon, a single valve for clos ing the lower end or said pressure cylinder and for controlling the flow of fluid from said outer cylinder, and means for operating said latching means, said valve and said inner cylinder to take a core as fluid is discharged from said outer cylinder through said valve, and seal the core in said outer cylinder, said operating means including a stufiing box in the upper end of said outer cylinder and a rod extending through the same to'transmit force to said inner cylinder.

EARL BABCOCK, 

